Heretofore, as disclosed e.g. JP-P-1-98340A, corresponding to U.S. Pat. No. 4,943,975, in a direct spread spectrum communication system using a correlator such as a surface acoustic wave (SAW) convolver, in the case where a pseudo noise code (hereinbelow abbreviated to PN code) is used as spreading code, it is necessary to use a code synchronizing system in the receiver.
A pseudo noise code generator (hereinbelow abbreviated to PNG) used in the system described above is a device as disclosed, corresponding to U.S. Pat. No. 4,845,726, in JP-P-63-l8836A and the synchronizing system using such a PNG has drawbacks as indicated in following items (1) to (3).
(1) In order to generate a head bit pulse of a PN code outputted by a PNG 1, as indicated in FIG. 2, a high speed counter is necessary for the counter 2, which counts the PN code length.
(2) In order to generate sampling pulses sampling correlation pulses from correlation spikes outputted by an SAW convolver, which are used in a digital phase lock loop (DPLL) for holding the synchronization, apart from a counter 3, a high speed shift register is necessary as the shift register, as indicated in FIG. 4.
(3) A counter and a shift register, which are high speed circuits, as indicated in (1) and (2), have a drawback that the number of elements and electric power consumption are increased, e.g. when they are formed in an IC.